Bug 1464132

Summary:	Booting/shutting down VM with vhost-user and IOMMU when backend does not support IOMMU will cause qemu error
Product:	Red Hat Enterprise Linux 7	Reporter:	Pei Zhang <pezhang>
Component:	qemu-kvm-rhev	Assignee:	Maxime Coquelin <maxime.coquelin>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Pei Zhang <pezhang>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	7.4	CC:	ailan, chayang, juzhang, maxime.coquelin, michen, pezhang, virt-maint, xiywang
Target Milestone:	rc
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2018-01-15 09:35:49 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1473046

Description Pei Zhang 2017-06-22 13:36:58 UTC

Description of problem:
Boot guest with vhost-user and vIOMMU, when the backend does not support IOMMU,
Qemu terminal will repeat popup error info: 
"qemu-kvm: failed to init vhost_net for queue 0
vhost lacks feature mask 8589934592 for backend "

Then rebooting VM will cause qemu segmentation fault.


Version-Release number of selected component (if applicable):
3.10.0-685.el7.x86_64
qemu-kvm-rhev-2.9.0-12.el7.x86_64
libvirt-3.2.0-14.el7.x86_64
openvswitch-2.7.0-8.git20170530.el7fdb.x86_64
dpdk-17.05-2.el7fdb.x86_64


How reproducible:
100%


Steps to Reproduce:
1. Start ovs

2. Boot VM with vhost-user and vIOMMU, qemu terminal will repeat promote error info.
/usr/libexec/qemu-kvm \
-name guest=rhel7.4_nonrt \
-machine q35,kernel-irqchip=split \
-device intel-iommu,device-iotlb=on,intremap \
-cpu host \
-m 8192 \
-smp 6,sockets=1,cores=6,threads=1 \
-device pcie-root-port,id=root.1,slot=1 \
-device pcie-root-port,id=root.2,slot=2 \
-device pcie-root-port,id=root.3,slot=3 \
-object memory-backend-file,id=ram-node0,prealloc=yes,mem-path=/dev/hugepages,share=yes,size=8589934592,host-nodes=1,policy=bind \
-numa node,nodeid=0,cpus=0-5,memdev=ram-node0 \
-drive file=/home/images_nfv-virt-rt-kvm/rhel7.4_nonrt.qcow2,format=qcow2,if=none,id=drive-virtio-disk0,cache=none,aio=threads \
-device virtio-blk-pci,scsi=off,bus=root.1,drive=drive-virtio-disk0,id=virtio-disk0 \
-chardev socket,id=charnet1,path=/tmp/vhostuser0.sock,server \
-netdev vhost-user,chardev=charnet1,id=hostnet1 \
-device virtio-net-pci,mq=on,netdev=hostnet1,id=net1,mac=88:66:da:5f:dd:12,bus=root.2,iommu_platform=on,ats=on \
-chardev socket,id=charnet2,path=/tmp/vhostuser1.sock,server \
-netdev vhost-user,chardev=charnet2,id=hostnet2 \
-device virtio-net-pci,mq=on,netdev=hostnet2,id=net2,mac=88:66:da:5f:dd:13,bus=root.3,iommu_platform=on,ats=on \
-monitor stdio \
-vnc :2 \
-netdev tap,id=hostnet0,vhost=on \
-device virtio-net-pci,netdev=hostnet0,id=net0,mac=88:66:da:5f:dd:11 \

qemu-kvm: failed to init vhost_net for queue 0
vhost lacks feature mask 8589934592 for backend
...

3. Reboot VM, qemu core dump
...
vhost lacks feature mask 8589934592 for backend
qemu-kvm: failed to init vhost_net for queue 0
Segmentation fault



Actual results:
Boot VM cause qemu repeat popup error info, and reboot VM will cause qemu core dump.

Expected results:
When the backend does not support IOMMU, probably qemu should give some friendly warning message. And qemu should not core dump when reboot the VM.


Additional info:
1. This issue was found when verifying bug[1].
[1]Bug 1451862 - IOMMU support in QEMU for Vhost-user backend 

2. As dpdk does not support IOMMU, so set 7.5 flag.

Comment 1 Maxime Coquelin 2017-11-16 14:00:48 UTC

Hi Pei,

Could you please retry with dpdk v17.11-rc4 tag?

Testpmd's cmdline requires a new Vhost PMD parameter (iommu-support):
--vdev 'net_vhost0,iface=/tmp/vhost-user1,iommu-support=1'

Thanks,
Maxime

Comment 2 Pei Zhang 2017-11-20 09:59:38 UTC

(In reply to Maxime Coquelin from comment #1)
> Hi Pei,
> 
> Could you please retry with dpdk v17.11-rc4 tag?
> 
> Testpmd's cmdline requires a new Vhost PMD parameter (iommu-support):
> --vdev 'net_vhost0,iface=/tmp/vhost-user1,iommu-support=1'

Hi Maxime,

With dpdk-17.11.tar.xz, qemu core dump issue has gone. Thanks.

Versions:
dpdk-17.11.tar.xz
qemu-kvm-rhev-2.10.0-6.el7.x86_64
3.10.0-784.el7.x86_64

testpmd command line:
# /root/dpdk-17.11/x86_64-native-linuxapp-gcc/build/app/test-pmd/testpmd \
-l 1,3,5 --socket-mem=1024,1024 -n 4 \
-d /root/dpdk-17.11/x86_64-native-linuxapp-gcc/lib/librte_pmd_vhost.so.2.1 \
--vdev 'net_vhost0,iface=/tmp/vhost-user1,iommu-support=1' -- \
--portmask=3 --disable-hw-vlan -i --rxq=1 --txq=1 \
--nb-cores=2 --forward-mode=io


Best Regards,
Pei


> 
> Thanks,
> Maxime